2008 Toyota Sienna AWD Tires

metmdx

I know that it is 'recommended' by every tire shop and dealer I've talked with, but can somebody give me a definitive reason other than "handling characteristics' why i can't have different brands on front and rear? These runflats are expensive, and due to a bizarre set of circumstances, I wound up with Bridgestone EL400 on the rear and Pirelli P7 on the front on my 2008 Sienna which only has just under 80K miles on it. I have an extra P7 brand new in the garage which i would pair with a 2nd to replace on the front rather than purchase 2 Bridgestones and be stuck with a brand new useless tire in the garage.
Thanks, metmdx

capriracer

You have to realize that *Handling Characteristics* is one of 2 correct answers.

Ya' see, if you mix brands - or even different models of the same brand - there is a possibility that the new tires will behave quite differently than the old ones. What could result is a vehicle that behaves unpredictably, especially in an emergency situation - and that could include losing control of the vehicle.

I use the words *possibility* and *could* because unless one tests that particular combination, it is not known what will happen. Plus, to test would require the destruction of a complete set of tires - way too expensive compared to benefit.

Lawyers absolutely love these situations because if anything bad happens - even if it is the driver's fault - it can be attributed to the tire dealer for not following the industry standard rules.

The second reason has to do with rolling diameter. There is no regulation that says that a given size tire must fall within a certain tolerance for diameter - and some AWD systems will fail if the tires aren't within a small tolerance. Replacing an AWD unit can be quite expensive and since vehicle manufacturers don't publish tolerances, the tire dealer should follow the industry standard rule that all tires have to be the same make. model, and state of wear.

metmdx

Very specific and on-point reply. Thank you for the input.
metmdx

DLu

changing weather conditions make a big difference as well -- rain, standing water, snow, ice, etc. If the front tires are different from the rear tires, your can lose control when trying to turn, stop, avoid hydroplaning, stay in control; this is especially true at highway speeds.